Digital protective relays used for protection, monitoring and control of electric power systems have the processing capability of performing a substantial number of protection functions and storing information concerning faults and other events which occur during the operation of the power system. Typical information developed by such digital relays include oscillographic information as well as the voltage, current and related values from the power line occurring before, during and after a particular event. Voltage and current values from the power line are sampled at regular intervals, e.g. 16 samples per power system cycle. Still other information developed by some relays in typical operation includes the location of faults, the relay settings and the condition of relay targets.
In an integrated protection system, such as shown generally in FIG. 1, information developed by a digital relay is typically transmitted, either automatically or manually, from individual relays 12—12 present at a substation 13, for instance, to a remote terminal unit (RTU) or communication processor 14, and from there to a remote device 16, such as a master computer, where system operators use the information to control the operation of the power system.
The information from the relays can also be moved to another remote computer 18 from the RTU/communications processor 14 or from master computer 16. The information provided to the master computer 16 is used for analysis and is usually stored. In existing systems, for instance, the “system operation” information developed by relays in operation in response to power line conditions is not stored at the digital relay, but rather is transmitted to a remote system-based computer for analysis and storage.
There are a number of human interactions with a protective relay which can occur during operation of the relay. As an example, a system operator will visit a power substation and inspect the “target” indications (lights) on the front panel of the relay, which indicate particular actions which have been taken by the relay. The operator will reset the targets and typically will indicate such action in a separate log of some kind. The same may be true if the operator changes the relay's operational settings. These and other actions taken by the operator may be entered into a separate handwritten log at the relay location (the substation), or in some cases entered into a computer which then transmits the information to a remote location, such as to the master computer.
However, this record of actions taken by an operator is often incomplete or may be missing entirely. An operator reviewing the log at a later visit is often unable to accurately determine what actions, if any, have been taken with the relays at the substation, including date and/or time of the action. All of this information is important relative to analyzing operation of the relays and the condition of the power system. Further, if any such information or partial information has been transmitted to a remote computer, it is difficult and time-consuming for the operator to retrieve the information at the substation location; hence, such retrieval may not be accomplished, and any analysis/review of previous actions is left undone. It is thus desirable to have more complete, accurate and accessible information concerning human interactions relative to the protective relay and its operation.